In medical testing and processing, the use of robotics may minimize exposure to, or contact with, bodily fluid samples (otherwise referred to as “specimens”) and/or may increase productivity. For example, in some automated testing and processing systems (e.g., clinical analyzers) sample containers, such as sample (blood) collection tubes, sample cups, vials, small sample cups (SSCs), and the like, may be transported to and from testing and/or processing systems in sample racks (sometimes also referred to as “cassettes”). The sample racks may contain an array of differently-sized sample containers (e.g., different height sample collection tubes). Furthermore, some or all of the sample collection tubes may include an SSC inserted in a top thereof. SSCs are used when only a small amount of bodily fluid sample has been allocated for a particular process or test. Generally, such SSCs have a much smaller volume-holding capacity than a sample collection tube. A depth and diameter of the SSC are also generally less than the sample container into which they are received. In other embodiments, a sample collection tube may be received in an insert received in a sample rack.
Such transportation of the sample rack may be accomplished by the use of an automated mechanism, which may include a belt or other transportation lane mechanism. The sample rack may be moved from one location to another in relationship to the testing or processing system. At one or more locations along the system, the sample rack may stop, and an image of each sample container in the sample rack may be obtained by an imaging system. At a separate location, an aspiration station, including a moveable aspiration nozzle, may also be provided. At the aspiration station, the nozzle tip of the moveable aspiration nozzle is inserted into the sample container (or SSC) to a desired depth and sample fluid is aspirated therefrom. The sample fluid may then be transferred to another location (e.g., to a cuvette or other reaction vessel) to carry out testing or further processing of the sample fluid thus aspirated.
Although, in general, the location of the nozzle tip in space is theoretically known by a controller of the system, some inaccuracies or deviations from the theoretical position may come into play due to tolerance stack-ups upon system assembly. Such inaccuracies may result in inaccurate positioning of the nozzle tip. This may cause collisions or jams between the nozzle tip and the sample containers or SSCs. Additionally, inaccurate positioning may not allow aspiration of the entire available sample. Furthermore, inaccurate positioning may cause portions of the sample that are undesirable to be aspirated, such as sediment at or very near the bottom of the sample container or SSC. Accordingly, methods and systems that may improve accuracy of positioning of nozzle tips relative to sample containers, especially SSCs, being conveyed to and from testing and processing systems are desired.